This invention relates to an apparatus for grinding the finish of piston rings, and more particularly to improvements in an apparatus provided with sleeve means which are subject to wear after grinding the finish of an outer peripheral surface of numerous piston rings.
The accuracy in grinding the finish on the outer peripheral surface of piston rings will have a significant effect on the performance of the piston rings, particularly on sealing requirements thereof. Therefore, it has been necessary, during production of the piston rings, to give special attention to the grinding finish step in order to achieve the finest quality of finish on the workpiece.
It is a conventional and effective practice to apply the finish by holding the piston ring within a sleeve and vertically moving the ring in frictional engagement with the grindstones or diamond lapped tools in the sleeve. More specifically, the self-exerted outward expansion of the piston ring to the ground presses the outer surface of the piston ring onto the inner surface of the sleeve with the nominal dimension of the piston ring being substantially equal to the internal diameter of the sleeve.
A serious problem results in that numerous piston rings have to be finished and rapid wearing down the grindstones fixed to the internal surface of the sleeve results in enlarging the internal diameter thereof.
When the grindstones are worn down to the point that grinding effeciency suffers, no sleeve can provide uniform tolerances of finished piston rings. As a result, the conventional sleeve has to be replaced with to a new sleeve which is of the internal diameter equal to the nominal dimension of the piston ring. Such an exchange of the sleeves may considerably decrease the working efficiency due to interruption of the finishing step operation and substantially increases manufacturing cost.